# Real-time matchmaking channel.
#
# Client flow:
#   1. Connect: ws(s)://host/cable?token=<JWT>
#   2. Subscribe to "MatchmakingChannel"
#   3. Send { action: "start" } to enter the queue
#   4. Receive { type: "matched", ... } or { type: "timeout" }
#   5. Disconnecting (or sending { action: "stop" }) cancels the search.
class MatchmakingChannel < ApplicationCable::Channel
  def subscribed
    # NB: must mirror MatchmakingService.broadcast, which uses
    # broadcast_to(user_id) → "matchmaking:<id>". stream_for(current_user)
    # would use the GlobalID-based name and never receive those broadcasts.
    stream_from "matchmaking:#{current_user.id}"

    # If a match was found while this user had no subscription
    # (e.g. brief reconnect), deliver it now — exactly once.
    if match = MatchmakingService.claim(current_user.id)
      transmit(match)
    end
  end

  def start(_data)
    MatchmakingService.enqueue(current_user.id, rating: current_user.rating)
  end

  def stop
    MatchmakingService.cancel(current_user.id)
  end

  def unsubscribed
    MatchmakingService.cancel(current_user.id)
  end
end